.pythonrc

"""
A custom configuration for interactive Python sessions.

Features:
- Colored PS1 and PS2 prompts.
- Persistent readline history.
- Four spaces instead of tabs.
- Tab completion in any Python.

Docs:
- https://tiswww.case.edu/php/chet/readline/readline.html
- https://docs.python.org/3/using/cmdline.html#envvar-PYTHONSTARTUP
- https://docs.python.org/3/library/sys.html#sys.ps1
"""
import atexit
import os
import readline
import rlcompleter
import sys

# We need RL_PROMPT_START_IGNORE and RL_PROMPT_END_IGNORE to display correctly.
sys.ps1 = "\001\033[34m\002>>>\001\033[0m\002 "  # Blue PS1.
sys.ps2 = "\001\033[35m\002...\001\033[0m\002 "  # Magenta PS2.

# Keep 10,000 lines of history at ~/.python_history.
history_length = 10000
history_file = os.path.join(os.environ["HOME"], ".python_history")

# Enable tab completion. This is the default in Python 3.
init_line = "tab: complete"

# Copy the existing readline completer.
_default_completer = readline.get_completer()


def spaces_for_tabs(text, state):
    """Insert four spaces instead of tab. Use ctrl+v, tab for real tab."""
    if text:
        return _default_completer(text, state)
    elif state == 0:
        return "    "
    else:
        return 0


try:
    # Read the history file. Don't fail if we can't.
    readline.read_history_file(history_file)
except IOError:
    pass

# Set our readline customizations.
readline.set_history_length(history_length)
readline.set_completer(spaces_for_tabs)
readline.parse_and_bind(init_line)

# Write history when the interpreter exits.
atexit.register(readline.write_history_file, history_file)

# Clean up all our imports and definitions.
del (
    atexit,
    os,
    readline,
    rlcompleter,
    sys,
    history_length,
    history_file,
    init_line,
    spaces_for_tabs,
)